In some semiconductor manufacturing processes, wafer processing chambers or reactors are used to process wafers from which integrated circuits are made. During the manufacturing process, a wafer is placed on a wafer holder (or susceptor). After the wafer has been placed on the wafer holder, it is placed in a processing chamber or reactor where a process, which has non-steady state temperatures, is performed using backside lamps. The backside lamps may include one or more lamps placed under the wafer holder to heat the wafer holder and the wafer.
For example, a rapid thermal process (RTP), using backside lamps, may be performed to deposit film layers on the wafer. This may be referred to as chemical vapor deposition (CVD). As the CVD process is carried out, the amount of film deposited on the wafer may vary as a function of the temperature of the wafer. The wafer temperature may not be uniform for a variety of reasons. For example, the wafer temperature may not be uniform because the wafer edge transfers heat to the underlying wafer holder, thereby causing a temperature difference between the wafer edge and the wafer center. As such, the uneven wafer temperature results in uneven/varying film deposition that ultimately adversely affects the performance of the integrated circuit made from the wafer. Temperature uniformity can also be important for other non-steady or RTP temperature processing such as annealing, doping, etching, and other processes. Accordingly, there is a need for a wafer holder (susceptor) that more uniformly controls wafer temperature during non-steady state conditions.